Controller for motors.



No. 673,9). Patented m 14, mm.

c. w. KRAGH.

CONTROLLER FOR MOTORS.

'Applicntion filed. Apr. 14, 1900.)

2 Shooh-Shoot I.

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UNITED STATES PATENT union.

CHRISTIAN W. KRAGH, OF MADISON, WISCONSIN, ASSIGNOR TO THE NORTH- ERN ELECTRICAL MANUFACTUR CONTROLLER SPECIFICATION forming part of Letters ING COMPANY, OF SAME PLACE.

FOR MOTORS.

Patent No. 673,910, dated May 14, 1901.

To (ti/7, whom it may concern.-

Beit known that LOHRISTIAN W. KRAGH, a citizen of the United States, residing at Madison, in the county of Dane and State of WViscousin, have invented a certain new and useful Improvement in Controllers for Motors, of which the following is a specification.

My invention relates to controlling devices for motors, and has for its object to provide a new and improved device of this description.

My invention is illustrated in the accompanying drawings, wherein- Figure 1 is a diagrammatic view illustrating my invention. Fig. 2 is a view showing the controllerproper with case omitted. Fig. 3 is'a section of the resistance-coil.

Like letters referto like parts throughout the several figures.

It has heretofore been the practice to provide the resistance used in controlling motors with a series of contact-points arranged in a circle or the arc of a circle, said contactpoints being of comparatively small area and being placed upon a flat surface, a contact- -arm being provided which moves'in the arc of a circle, so as to be moved from one con-v tact to another. When such a construction is used in connection with motors carrying heavy curr entssuch, for example, as motors for cranes and the likethese contacts, on account of their small area, are liable to be injured by the current, so as to become uneven and objectionable in many ways. In this construction there is no way of properly remedying these evils or smoothing down the contacts when they become burned orinjured. Another objection to such a construction is that the contacts must be given a large dimension laterally so as to get anything like a practical contact area, and they must also be separated quite a distance, and hence only comparatively few contact-points can be used.

One of the objects of my invention is to provide a controller for motors in which these objectionable features'will be obviated.

' Referring now to the drawings, I have shown in Fig. 1 the controller proper, A, connected in circuit with the motor B, said motor being connected in circuit with the generator C: The controller proper consists of a suitable resistance placed in the casing A. This resistance may be made up in any desired manner and as illustrated in Fig. 2 consists of a series of coils A of sheet-resistance placed upon a central holding part A the several sections of coils being separated by suitable non-conducting material, such as asbestos or the like, the coils being provided with suitable contact-points A to which conductors A may be connected, so as to divide the resistance up into sections in a predetermined manner. These conductors are connected to a series of stationary contact-bars D, separated by suitable insulating material D. These contact-bars are so positioned as to form a circle or the arc of a circle, the device when forming a complete circle having the appearance of a commutator. A suitable controller-arm E is mounted in proximity to the contact bars D and, as herein shown, is connected with a rotatable shaft E, which passes through the central holding part A Connected with the controller-arm E are one or more movable contacts or brushes E which engage the contact-bars D as the controller-handle is moved. The movable contacts may be of any desired material. This construction permits these movable contacts to be made of carbon, and they may be ordinary carbon brushes connected With a suitable brush-holder E attached to the controller-arm. The parts may be arranged so that the brushes or movable contacts normally rest upon a dead-point. When moved away from that dead-point, they first cut in all the resistance and then gradually cut the resistance out in a predetermined manner. It will be seen that this construction is the best possible arrangement for obtaining a large number of contact-bars D and still permitting said bars to have a sufficient carrying capacity. Instead of being limited to ten or fifteen contact-points, this construction permits the contact-points to be increased to one hundred or more, and hence the resistance can be divided up so as to get the best results.

contact passes around the periphery of. the device or the outer face of the contact-bars, and hence if said bars are thin, so as to get a large number of contacts, a proper amount It will be noted that the movable IOO of metal may be had to obtain the desired carrying capacity by lengthening the bars, thus increasing the contact area. When the contact-points are placed upon a flat surface, they can only be extended by increasing the diameter of the device; but in my construction, since the contact-face is parallel to the; axis instead of perpendicular to it, such contact-surface may be lengthened any desired amount without inconvenience. When this construction is used, it will be seen that a multiplicity of contacts may be had, so as to divide the controller resistance into a large number of sections,and that asufficient contact area may be obtained to prevent. the burning or destruction of the contact-bars. It will also be seen that even if these bars become injured by accident or for any other reason they can be turned down, so as to again provide a smooth contact-surface along the .entireouter face of the bars. The controller may be located at any desired point with relation to the motor.

I have shown aparticular construction embodying my invention; but it is of course evident that the parts may be varied and that different forms of resistance may be used and other changes made without departing from the spirit of my invention, and I therefore do not limit myself'to the construction shown.

I claim v In a controller, the combination-of a supporting part with a series of conductors coiled CHRISTIAN W. KRAGH.

Witnesses:

AUGUST J. BUENZLI, FRANK L. STAGG. 

